1. Field of the Invention
Aspects of the present invention relate to a digital broadcast transmitter/receiver and a signal processing method thereof, and more particularly, to a digital broadcast transmitter/receiver and a signal processing method thereof which can improve the receiving performance of the receiver by inserting a known sequence into stuff bytes added to a dual stream in the digital broadcasting transmitter which transmits the dual stream, and transmitting the dual stream with the inserted known sequence.
2. Description of the Related Art
An ATSC (Advanced Television Systems Committee) VSB system, which is an American-type digital terrestrial broadcasting system, is a signal carrier type broadcasting system. The system uses a field sync signal in the unit of 312 segments. Accordingly, the conventional digital broadcast receiver has a deteriorated receiving performance in an inferior channel environment, and especially in a Doppler-fading channel environment.
FIG. 1 is a block diagram illustrating the construction of a transmitter of a general American-type digital terrestrial broadcasting system. The digital broadcast transmitter of FIG. 1 is an EVSB (Enhanced VSB) system proposed by Philips, and can provide and transmit a dual stream obtained by adding robust data to normal data of the conventional ATSC VSB system. The digital broadcast transmitter of FIG. 1 includes a randomizer 110 for randomizing data. A first RS (Reed-Solomon) encoder 120 RS-encodes the output of the randomizer 110. A packet formatter 130 interleaves robust data of the encoded data, reformats the packet at a ½ rate, inserts a PID (Packet Identifier) value into the packet, and multiplexes the packet and normal data. An interleaver 140 interleaves the data from the packet formatter 130. A trellis encoder 150 performs an enhanced coding of the robust data at the output of the interleaver 140 and performs a ⅔-rate trellis encoding of the data. A controller 160 outputs a signal for controlling the normal data and the robust data. A second RS encoder 170 performs RS re-encoding of the enhance-coded robust data so as to be compatible with a conventional receiver and replacing a parity. A multiplexer 180 inserts a field sync signal and a segment sync signal into the trellis-coded data. A modulator 190 adds a pilot signal to the output signal of the multiplexer 180, and performs a VSB modulation and RF up-conversion of the multiplexed data.
FIG. 2 shows the format of the dual stream type data output from the transmitter of FIG. 1. Referring to FIG. 2, a dual stream type transport stream packet is composed of a 4-byte transport stream header and a 184-byte payload data. The normal data and the robust data are arranged in the payload data at predetermined intervals.
Referring to FIG. 1, the normal data and the robust data are multiplexed and input to the randomizer 110, according to the dual stream mode for transmitting the normal data and the robust data through one channel. The input data is randomized by the randomizer 110, and is input to and RS-encoded by the first RS encoder 120 so as to correct bit errors occurring due to the channel. The RS-encoded data is input to the packet formatter 130, and a robust process is performed in a manner that robust data of the encoded data is interleaved and reformatted to a packet at a ½ rate, and a PID (Packet Identifier) is inserted into the reformatted packet. This packet and normal data are then multiplexed and output to the interleaver 140. The data output from the packet formatter 130 is interleaved through the interleaver 140, and then is input to the trellis encoder 150. The robust data of the reformatted data is enhanced-coded, and then is trellis-encoded at a ⅔ rate through the trellis encoder 150. The enhance-coded robust data is then re-encoded through the second RS encoder 170 so as to be compatible with the existing receiver, and a parity replacement is performed with respect to the re-encoded data. The replaced parity is input to the trellis encoder 150. The signal having passed through the multiplexer 180 for inserting a field sync signal and a segment sync signal into the trellis-encoded data, after a pilot signal is added thereto, is VSB-modulated and RF-up-converted through the modulator 190. Here, the normal data and the robust data are controlled according to a control signal output from the controller 160.
As described above, the American-type digital terrestrial broadcasting system in FIG. 1 is constructed so that it can produce a dual stream by adding the robust data to the normal data of the existing ATSC VSB system. However, in spite of the dual stream transmission through the addition of the robust data to the normal data, the American-type digital terrestrial broadcasting system in FIG. 1 has the problem that its receiving performance in a multi-path channel is hardly improved due to the transmission of the existing normal data stream. That is, the existing digital terrestrial broadcasting system has little improvement of the receiving performance according to the improvement of the normal stream. Also, according to the American-type digital terrestrial broadcasting system, the improvement of the receiving performance in a multi-path environment is not great even with respect to the robust stream.